(Supported in part by NIEHS Superfund ESO4913 to D. Carpenter). The adsorption of PCB's into river clay depends upon the size, geometry, and composition of the clay particles. We are using the HVEM and IVEM for imaging, electron diffraction, and energy-dispersive x-ray microanalysis to characterize the particles. We hope to be able to locate the actual PCB adsorption sites on the particles. We are studying particles as collected, and also particles to which PCB's have been added. We have recorded many images, diffraction patterns, and x-ray spectra from the particles. This data will be included with a presentation at RPI promoting the BMIRR this Autumn.